Exemplary embodiments of the present invention relate to aviation technology. In particular, exemplary embodiments of the present invention relate to actuator technology for aerodynamically active elements of an aircraft. Furthermore, exemplary embodiments of the present invention relate to an actuator element with a reversible decoupling device, an actuator arrangement as well as an aircraft, particularly an airplane or helicopter.
Actuators are used in aircraft to mechanically move aircraft elements and to change their position or location. For airplanes, these are for example rudder surfaces or wing elements to influence the lift behavior of the airplanes. For helicopters, this can pertain for example to the various rotor blade positions by means of a swashplate.
Such actuators are conventionally designed as hydraulic elements, since this technology has been mastered for a long time and is less prone to faults. In the event of a malfunction, conventional hydraulic actuators can usually still be moved; in other words, they are not jammed in the event of a malfunction.
Due to the increased electrification of aircraft, it is desired to replace hydraulic actuators, which possibly require a hydraulic system running throughout the entire aircraft, with electric actuators. These can be supplied in a purely electrical manner, wherein such electrical lines are normally simpler to install and maintain in an aircraft than hydraulic lines. In addition, the electrical transmission of power or energy makes a weight decrease possible compared to a hydraulic system. Generating movement by such an electric actuator can now also be executed solely electrically, for example using a suitable drive by means of an electric motor; or however, a local hydraulic system can be provided at the actuator, particularly a hydraulic system arranged in the actuator system, the hydraulic system having to also be supplied with electrical energy only from the outside.
FIG. 1a depicts a schematic illustration of an electromechanical actuator.
As illustrated in this example, two motor elements 1 are linked to drive unit 8 of actuator element 3, using a suitable linkage consisting of a motor shaft 2a and a suitable transmission 2b. Drive unit 8 is changeable in its length I, particularly in its distance between the two linkage points 5a,b, so that a length change of drive unit 8 of actuator element 3 modifies the distance between linkage points 5a,b. By means of a suitable restraint between elements, a moving or tilting of an aerodynamically active structure is possible. Drive unit 8 consists of a first drive element 8a and a second drive element 8b, constructed, for example, as a ball screw drive 8 with a ball nut 8b and a ball spindle 8a. By rotating ball spindle 8a, ball nut 8b can be displaced on it, so that the rotation of ball spindle 8a provides a length change of drive unit 8 and thus of actuator element 3 or a change in the distance between linkage points 5a,b. In the event of a defect of an actuator element, particularly for mission-critical aerodynamically active surfaces, one must ensure that these can at least still be moved despite the defect. In the event that an actuator element fails, depending on actual use, usually a certain redundancy is provided. In the case of tail units or rudders, a second actuator element can be arranged in a force-parallel manner to the first one for example so that the position change of the aerodynamically active surface can be detected by one of the two actuator elements or also by both together.
Now should an actuator element of the two parallel actuator elements fail, then the other one can at least maintain the function. However, particularly relevant in this context are defects of actuator elements that subsequently no longer allow a length change to be executed; for example the breaking of the ball of the ball screw drive can possibly jam the ball spindle and the ball nut against each other so that a length change of the actuator element is no longer possible. In such a case, control of the aerodynamically active surface can also not be executed by the parallel-arranged actuator element. In a worst case scenario, the aircraft would thus no longer be controllable and would possibly crash. To keep electromechanically actuator elements changeable in their length at least by an external force, including in a malfunction situation, decoupling devices or decoupling mechanisms can be integrated into the actuator elements, which remove the blockage in a malfunction by decoupling the jammed actuator element and thereby ensure that the aerodynamically active surface remains movable and controllable by the force effect of the parallel-arranged element.
FIG. 1b depicts an example of such an actuator element. Ultimately, the embodiment of FIG. 1b differs from FIG. 1a only by the provision of a decoupling device 6. Decoupling device 6 thereby not only decouples the two drive elements 8a,b from each other; instead, a decoupling is undertaken in such a manner that a decoupling of the contact points 5a,b results, wherein one of the contact points is also essentially connected in a decoupled state with both drive elements of the drive unit, while the connection of a drive element to the second contact point 5b is released. The length of an actuator element can hereby change regardless whether a mechanism of the drive unit, for example the first drive element 8a to the second drive element 8b, is jammed.
One aspect of the present invention provides a special design of a reversible decoupling device for an electromechanical actuator element.
According to a first embodiment of the present invention, an actuator element has a drive unit with a first drive element and a second drive element, wherein the first drive element and the second drive element functionally interact in such a manner to effect a change in length of the actuator element, wherein the actuator element has a decoupling device, wherein the actuator element has two linkage points, whose span can be set by the length change of the actuator, wherein one of the drive elements is connected in an essentially direct-action manner with the other linkage points, wherein the span of the two linkage points in a coupled state of the decoupling device can be adjusted by the actuator element and wherein the span of the two linkage points in the decoupled state of the decoupling device can be changed by subjecting the linkage points to an external force. The decoupling device has a decoupling mechanism with a drive element, a form-fitting element, and a retaining element, wherein the retaining element is set up to take a first position in which the form-fitting element is in a closed state, and wherein the retaining element is set up to assume a second position in which the form-fitting element is in an open state. The drive element is set up to displace the retaining element between the first position and the second position, whereby the form-fit of the form-fitting element can be reversibly released and fixed, wherein the decoupling mechanism functionally decouples the output piston from a drive element of the actuator element in such a manner that the change in length of the actuator element is made possible independent of the drive unit, particularly without any functional decoupling of the first drive element and second drive element.
According to another embodiment of the present invention, an actuator arrangement includes at least two actuator elements according to the present invention, wherein the at least two actuator elements are arranged in a force-parallel manner so that a length change of the actuator arrangement can be effected by an actuator element alone or by both actuator elements simultaneously.
According to another embodiment of the present invention, an aircraft, particularly an airplane or helicopter, includes an actuator arrangement according to the present invention and/or an actuator element according to the present invention.
Conventional actuator elements for actuating aerodynamically active elements have either no decoupling device or one that possibly provides only an irreversible decoupling or a decoupling that can only be re-coupled with great effort. Since electromechanical actuator elements with a decoupling device that control aerodynamically active elements may involve mission-critical elements, which in a malfunction could possibly result in the aircraft crashing, regular testing of a decoupling device and thus the simulation of the malfunction is desirable to ensure correct operation in the event of a malfunction. Electromechanical actuator elements, which cannot be re-coupled with little effort are thus possibly not testable at periodic intervals. It cannot be assured that a conventional decoupling device functions properly in an emergency, thereby ensuring that the flyability of an aircraft is maintained.
In contrast to this, the present invention provides an actuator element with a decoupling device, which after actuation can be transferred back into a coupled state in a simple manner. An actuator with such a reversible decoupling device can now be regularly inspected for proper functioning, for example during a comprehensive test prior to operating an aircraft. During the test, the decoupling device can thus be triggered under load the actuator element can thus be decoupled, whereby the worst-case scenario of the flight operation can be reconstructed. At the end of the test run, the still function-capable actuator element can simply be re-coupled and thereby makes its normal operating mode available.
Thus, according to the present invention an output piston is coupled with a drive unit of the actuator element in such a manner that the output shaft is connected in a form-fitting manner to a drive element of the drive unit. This represents the normal operating mode. The drive unit has a first drive element and a second drive element, which functionally interact in such a manner that the drive unit can provide a length change of the actuator element. The form-fitting coupling of the output piston to one of the drive elements provides for the length change of the actuator element. The two linkage points of an actuator element, which ultimately represent the effective length of the actuator element, can thus be arranged on the output piston on the one hand and on the actuator element itself on the other, for example on its housing. Thus, a linkage point is rigidly connected to the housing of the actuator element, while the second linkage point is linked via the output piston and is thereby connected to the drive unit. The output piston can be subjected to a translation movement, whereby the actuator element can be adjusted in its length.
In a coupled state of the decoupling device, the output piston is now connected to the drive unit or a drive element of the same in a form-fitting manner. In the event of a malfunction or decoupling, the form-fit between the output piston and the drive element of the drive unit may be released. In this way, the actuator element may experience a decoupling from the drive unit and output piston so that the length of the actuator element can be adjusted from the outside by means of a comparatively small amount of supplied power. In the event of a malfunction, in which the actuator element is thus decoupled, this, despite its defect, does not represent a jammed device, which could possibly lead to a negative influence on the controllability of an aircraft.
Such actuator elements are usually provided in the form of an actuator arrangement, which provides for a certain redundancy for controlling or positioning aerodynamically active elements. For example, two actuator elements can be arranged in a force- or effect-parallel manner so that the position and orientation of the aerodynamically active element can be separately effected by each of the actuator elements or however these may interact, whereby a force can be applied by both actuator elements. In the event of a malfunction, i.e., in the event that one of the actuator elements has a defect and is no longer able to function, or in a worst case scenario jammed so that a length change is no longer possible, the decoupling device according to the invention can decouple the actuator element in such a manner that a length change of the actuator element can be effected by an externally applied force. In this case, the defective actuator element could be decoupled and thereby does not represent any restriction regarding the controllability of the aerodynamically effective element for the parallel-arranged second actuator element, besides a slight amount of force expended for changing the length of the defective actuator element. In this way, the controllability of the aerodynamically active surface can continue to remain assured, despite the worst-case scenario of a jamming defect of one of the two actuator elements arranged in an effect- or force-parallel manner.
According to a preferred embodiment of the present invention, the drive unit may be designed as a ball screw drive, wherein the first drive element and the second drive element may be designed as a ball spindle and ball nut of the ball screw drive. For adjusting the length change of an actuator element, there are various implementation possibilities. Usually in the aviation segment, a configuration as ball screw drive or roller screw drive is selected, since these are comparatively robust and can transfer large forces in a low-friction and low-wear manner. A ball screw drive thereby normally consists of a spindle as well as a ball nut. Various implementations provide for the moving and rotating of the ball spindle, while a ball nut, secured against rotation, is displaced on the ball spindle. Another embodiment provides for the ball nut to rotate, while the ball spindle thereby completes a translation parallel to the axis of rotation.
According to another preferred embodiment of the present invention, the actuator element may also have a motor element, wherein the ball nut can be rotated when using the motor element, by means of which a length change of the actuator element can be executed through the translation of the ball spindle. According to another preferred embodiment of the present invention, the form-fitting element can be engaged with the output piston in a form-fitting manner so that the translation of the ball spindle causes a translation of the output piston. The present invention pertains particularly to an embodiment in which the ball nut rotates, while the ball spindle moves in a translational manner and the length of the actuator element is hereby adjusted. For a preferred decoupling of the drive elements of the drive unit, the decoupling device shall not undo the drive elements themselves if possible since this can possibly not be assured at all times, particularly in the event of a ball screw drive or planetary roller screw drive. To this end, a linkage point is connected to the drive unit, a second linkage point is connected via another element to the other drive element, while the decoupling device or the decoupling mechanism decouples a linkage, particularly a form-fitting one, of a drive element and another element to the linkage point in such a manner that a length-changing capability can be assured by means of an external force on the actuator element in a decoupled state, even if the first drive element and the second drive element are completely jammed, by undoing the connection between the drive element and other element. The decoupling device or the decoupling mechanism can thus be displaced preferably between a first state, a closed state in which the form-fitting element is closed, and a second state, an open state in which the form-fitting element has a released form-fit.
According to another preferred embodiment of the present invention, the spindle may be constructed as a hollow spindle, wherein the output piston is arranged inside the spindle. The actuator element of the present invention thus has a drive unit with a ball screw drive, particularly a rotating spindle nut, and a translationally moved spindle, to which an output piston is connected in a form-fitting manner using the decoupling mechanism, wherein the second linkage point is arranged on the output piston. The spindle can thus be constructed as a hollow spindle for example, in whose interior space the output piston is arranged. Without a form-fit of the form-fitting element, the output piston may essentially be freely displaceable inside the spindle, while the output piston in the form-fitted state of the form-fitting element is rigidly connected to the spindle and moves translationally with the spindle when the spindle nut rotates. In a form-fit-released stated, the output piston can be displaced with comparatively little force inside the spindle.
According to another preferred embodiment of the present invention, a form-fit may be provided in the first position of the retaining element between the output piston and the spindle, while in the second position of the retaining element, the form-fit between the output piston and the spindle is released and the output shaft can essentially be freely displaced inside the spindle. In this way, the retaining element enables one to simply switch between a form-fitting state and a non-form-fitting stated of the form-fitting element. The retaining element together with the form-fitting element thereby preferably does not act in the same force direction that may act on the actuator element due to a lengthening or shortening. Particularly preferred is the exertion of a force of the retaining element on the form-fitting element for providing the form-fit essentially vertically to the force provided by the actuator element based on its lengthening or shortening. The force provided by the retaining element can hereby essentially restrict itself to maintaining the form-fit and must not simultaneously be configured in such a stable manner as to resist the force, which the actuator element applies during lengthening or shortening. In this way, the force of the retaining element is decoupled from the force of the actuator element.
According to another preferred embodiment of the present invention, the form-fitting element may be constructed as a plurality of ball elements, wherein the output piston has recesses corresponding to the ball elements, wherein the retaining element is constructed as a sleeve element with recesses, wherein the sleeve element can be rotated using the drive element of the decoupling mechanism, wherein the sleeve element is set up in the first position to retain the ball elements in the recesses of the output piston to provide the form-fit between the output piston and spindle, and wherein the sleeve element is set up in the second position to accommodate the ball elements in the recesses of the sleeve element, so that the form-fit is released. The form-fitting elements can thus be displaced between a first, form-fitting position in which they are arranged in the recesses of the output piston and a second form-released position in which they are arranged in the recesses of the sleeve element. The sleeve element may thus execute a comparatively minor rotation and essentially be pivoted between a position in which the recesses of the sleeve element align with the form-fitting elements and a position in which the form-fitting elements are pressed or retained in the corresponding recesses of the output piston. A preferred release under load of the form-fit is hereby also possible, since due to the design of the form-fitting elements as ball elements, no jamming surfaces can occur. As soon as the recesses of sleeve element align with the ball elements, the latter are pressed, due to the form of the ball surface, out of the corresponding recesses of the output piston into the recesses of the sleeve element, and release the form-fit.
According to another preferred embodiment of the present invention, the actuator element may also have a housing and a sealing element arrangement, wherein the sealing element arrangement is set up in such a manner that the region of the form-fitting element, retaining element, output piston, and housing are essentially designed in a sealed manner so that in particular the region can be filled with a suitable lubricant. By means of such an arrangement, friction in the decoupling mechanism may be further reduced so that the actuation force of the decoupling mechanism is comparatively low. By means of the sealed design of the region of the sealing element arrangement, the latter may also be designed in an essentially maintenance-free manner.
According to another preferred embodiment of the present invention, the actuator element may also have rod seals, wherein when using the rod seals, a sealing effect is essentially provided for the lubricant also during a test. In this way, a test of the decoupling device can be repeatedly performed without possibly risking a function impairment in the event of a malfunction.
According to another preferred embodiment of the present invention, one of the linkage points may be arranged on a housing end of the actuator, while the other linkage point is arranged on the external end of the output piston. In this way, the two linkage points, which form the effective length of the actuator element, are arranged on opposite ends of the actuator element, while a simple decoupling of the output piston and elements provided in the actuator element, such as individual drive elements, can continue to be provided by the decoupling device or the decoupling mechanism.
According to another preferred embodiment of the present invention, the decoupling device may be decouplable in the course of a test and be re-couplable after completion of the test. A cyclic function test regarding the emergency coupling of the actuator element may hereby be performed and it may in particular be assured that the actuator element or its decoupling device can execute and not block a decoupling, even in a critical malfunction during flight.
According to another preferred embodiment of the present invention, the decoupling device may actuate the decoupling mechanism of the actuator element in the event of a defect of a drive unit or the ball screw drive or planetary roller screw drive of an actuator element, so that the actuator element is functionally decoupled, wherein the length change of the actuator arrangement can still be effected by the non-decoupled actuator element. The decoupling device according to the invention thereby ensures that the displaceability of an actuator element is assured from the outside even in the event of a fault, in a worst-case scenario in the event of the first and second drive elements jamming each other, so that the remaining, redundant, parallel-arranged second actuator element can continue to adjust the aerodynamically active element without being negatively influenced by the defective actuator element.
According to another preferred embodiment of the present invention, a conductive connection between the decoupling device and an aircraft can be routed solely to the stationary part of the decoupling device, so that a movement of the moveable part of the decoupling device does not require any movability of the conductive connection. By means of the mechanical transfer of the rotation through the pivoting sleeve from the stationary to the moveable part of the decoupling device or the element, all connections of the element, particularly including all connections of the decoupling device, each comprising connections for power transmission as well as for transmitting sensor signals from/to associated controllers/monitoring units can be attached in the stationary part of the element. In this way, one does away with the need for a special design of the cable harness for compensating for any relative motion that would be associated with additional effort, costs, and potentially reduced reliability.